ML20106D647

Forwards Response to GL 92-04, Resolution of Issues Related to Reactor Vessel Water Level Instrumentation in BWRs Pursuant to 10CFR50.54(f), in Ref to Reactor Water Level Indication Accuracy

ML20106D647
Person / Time
Site:	Oyster Creek
Issue date:	09/29/1992
From:	J. J. Barton GENERAL PUBLIC UTILITIES CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
C321-92-2267, GL-92-04, GL-92-4, NUDOCS 9210130131
Download: ML20106D647 (7)

Text

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e o GPU Nuclear Corporation Nuclear an:r>~

Forked R.ver, New Jersey 08731-0389 609 971 4000 Writer's Direct D.al Numb 9r.

C321-92-2267-September 29, 1992 US Nuclear Regult. tory Comission Attn: Document Control Desk Washington, DC 20555

References:

3. Generic Letter No. 92-04, " Resolution of the issues Related to Reactor Vessel Water Levoi Instrumentation in BWRs Pursuant to 10 U f' 50.54(f)", dated August 19, 1992.

2. BWROG-92074 to William T. Russell (NRC), BWROG Report, "BWR Reactor Vessel Water Level Instrumentation", dated August 28, 1902.

3. BWROG-92082 to U.S. Nuclear Regulatory Commission, Washington, DC 20555, " Reactor Vessel Water Level Instrumentation" dated September 24,1992.

Gentlemen:

Subject:

Oyster Creek Nuclear Generating Station Docket No. 50-219 Response to Generic letter 92-04 BWR Reactor Vessel Water Level Instrumentation Generic letter 92-04 requested all Boiling Water Reactor Licensees to respond to a list of specific questions from the NRC staff relating to reactor tvater level

, indication accuracy. Attachment 1 to this letter provides the plant specific GPU Nuclear response for the Oyster Creek-Nuclear Generating Station.-

As requesi.d on page 5 of GL 92-04, this letter is being submitted subject to the provisions of 10 CFR 50.54(f).

9210130131 920929 PDR ADOCKOSOOg9 ,

GPU Nuclear Corporation is a subsid:ary of Genera! PutAc Ut+ ties Cc'poratior. ,

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C321 92-2267 I Page 2 l l

l l

If you should have any q'testions or require further information, please contact {

Brenda DeMerchar.t, OC Licensing Ei.gineer at (609) 971-4642.

ry truly y rs,

/f J;hn J. Bay n

&/D~

ice Pres'f ant & Director Oyster Crl >k i

JJB/BDEM:Jc cc: Administrator, Region 1 Senior NRC Resident inspector Oyster Creek NRC Profact Manager SworntoandSubscribedbeforemethisQ$ dayoff h/1992.

A a No r JUDITH M.CROWE NotaryPuHicof Ng #C fI My Commission Expires l-

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ATTACHMENT 1 I

"In light of potential errors resulting trom the affects of ncn-condensible gas,  !

each licenseo should determines"  :

i NBC_REDVE11EQ_AnilDR_1(a) .

"The impact of potential levei indication errors on automatic safety system  ;

rer.ponso during all licensing Lasin transients and accidents." i GIMl_R W 931E There is no impact on automatic safety system response during licensing basis transients or accidents. The Lo and Lo-Lo reactor water signals for l RPS and ECCS systems are sensed by the hot leg Yarway instrument. As documented in the BWROG Ictter to the NRC staff, Yarways are not susceptible to the non-condensible gas phenomenon because of their geometric '

configuration.

The Lo Lo-Lo level setpoint used for Oyster Creek ADS actuation and RBCCW isolation is sensed by a cold leg instrument. The BWROG generic report (Ref. 2) reiterates previous conclusions with respect to cold leg "

instrumentation that safety system actuations occur prior to the introduction of errors associated with non-condensible gases coming out of solution. This conclusion is applicable to Oyster Creek.

NBLBfQuE.5JIP ACTION 1.ibJ _

"The impact of potential level indication errors on operator's short and long term actions during and after all licensing basis accidents and transients."

GIMLumDREE_.

As all protective functions are automatic and actuations based on level -

occur prior tc any degassification effects, there are no required operator . ,

actions during or after licensing basis accidents or transients, s

A review of the-Oyster freek UfSAR accidents and transients which result in rapid vessel depressurization was corducted. None of these accidents or transients require the operator to taKo aClions.

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C321-92-2267 '

Attachment l' Page 2 NRC REQVfJI1Q ACIl0!Lliql "The impact of potential level indication errors on operator actions prescribed in emergency cperating procedures or other affected procedures not covered in item b."

GtVN RESPQNSE_

1he Oyster Creek emergency operating procedures (EOPs) provide' appropriate guidance on how to address level indication discrepancies.

Operator guidance directs the operator to flood the reactor whenever confidence is lost in the level indication. The Emergency Procedure Guidelines are symptom-based procedures. The operators will assess the following symptoms to determine if the level indication can be trusted.

1. Conflicting information

2. All off-scale or unknown level indication

3. Reference leg temperature which could cause flashing The current procedural guidance is appropriate to deal with the non-cond9nsible issue given the present industry understanding. No revisions are currently planned.

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" Based upon the results of Item 1 ab.te, each licensee should' notify the NRC of-short term actions taken, such as:"

HBC_ REQUESTED ACT1.QtL2M

" Periodic monitoring of level 'instrunentation system leakage."

GPUN RESPONSE _

During the upcoming refueling outage which is currently scheduled to begin November 27, 1992, GPUN has scheduled testing of level instrumentation ,

equalizing valves for internal leakage.. GPUN will- evaluate the. data and continue this leakage testing in future outages if it is deemed necessary.

In addition, Equipment Operators will be instructed to look for evidence of external leakage- from vent, equalizing, drain and isolation valves while on -

normal walkdowns during plant operation.

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C321-92 2267  !

Attachment 1 Page 3 HRQ_Bf0 VESTED ACLLQfL21hl

" Implementation of procedures and operator training to assure that potential level arrors will not result in improper operator actions."

QPilN RE5fDliSL As stated previously, procedure revisions are not necessary at this time.

Existing onerator training continues to emphasize RPV flooding if level indication is in question. In addition, the operator practice of verifying level indication prior to termination of injection for level-control will be ,

reinforced.

MRG_REQUfJiLE_0 ACTION 3 "Each licensee should provide it plans and schedule for corrective actions, includi.g any proposed hardware modifications necessary to ensure the level instrumentation system design is of high functional reliability for long term operation. Since this instrumentation' plays an important role in plant safety and is required for both normal and accident conditions, the staff

. recommends that each utility implement its longer term actions to assure a level instrumentation system of high functional reliability at the first opportunity but prior to starting up after the next refueling outage commencing three months after the date of this letter."

GPUN RESPONSE GPUN is participating in BWROG efforts and endorses the conclusions of the-Generic BWR Owners Group Report provided in Reference 2 and the BWROG 1etter (reference 3).

Du-ing the next refueling outage (14R), GPUN has scheduled inspectinns and L verifications of cold reference leg level instrumentation.. This will include assessments of the steam leg insulation, slope, and configuratiot -

In addition, details of the condensing chamber type will be obtained. 'his geometric informatior 9111 be provided to the BWROG. Steam pipe insula, ion will be repaired as necessary.

During the cooldown for 14R subsequent scheduled cooldowns until this issue is resolved, the plant 7puter system will be used to' collect data from RPV la el and pressure instrumentation. As stated previously in the respnse to 2a, GPUN has scheduled testing for internal leakage on the ~ ,

equal 471ng valves during 14R. The results of this data collection effort r I

wi ' be orovided to the BWROG.

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C321 92-2267 Attachment 1 Page 4 GPUli is presently evaluatinq the installation of Resistance len.perature Detectors (RIDS) on the cold reference leg condensing chambers as a part of a data gathering offort in support of the BWROG test program. However, GPUN is not proposing any modifications to the plant level instrumentation system at this time. Ihroughout the Oyster Creek operating history, no level indication anomalies which would indicate non-condensible gas accumulation in the reference leg have been experienced. Therefore, it appears to be unnecessary to provide any modifications to the niant at this time. When the results or the BWROG ef forts to better understand the degassification

awnomena are completed, GFUll will re-evaluate if any changes are appropriate for Oyster Creek.

In contleslon, please note. g

1. A review of plant data and discussion with control room group shift ,

supervisors and control room operators, indicates that GPUf4 has not experienced the notching phenomenon associated with non-condensible gases coming out of solution.

2. The notching phenomenon ti mainly applicable to cold reference leo i nst rument at ion . The Oyster Creek reactor water level measurement configuration is noted on fable 1. Based on the above, it can be seen that the to anc; to-lo level protective actuations for OC are sensed via Yarway columns which are hot reference legs and not susceptible to the non-condensible gas issue witnessed by some utilities. The only _

cold reference leg instruments of safety significance are the Lo-Lo-Lo (ADS) function, and fuel zone indication.

3. lhe use of level instruments, including fuel zone level, is being evaluated f or other possitle options to determine reactor sater level before directing operator actions related to the discussion in Response to NRC Requested Action 2(b). For example, GPUN is evaluating guidance for the operators to wait for some level indication on the Yarway indicators before terminating injection flow.

4. GPUN is also participating in the EWROC generic program pertaining to the non-condensible gas issue. Until the results of the generic program are known, the benefit of any potential modification to Oyster Creek reactor water level instrumentation will not be understood.

I' i C321 92-2267 l Attachment 1 Page 5 TAtLE 1 INJlRVENI LEYILSEl_.E01HI/AANGE PR0dGII.YI_f.UNCJ10N/SERVICI Yarway .1, to

• Reactor Trip (Hot Ref. Leg) ,

a Range: 86" to 2. Lo-lo Recire Pump Trip '

186" TAf

• Reacto. Isolation a Alt. Rod Injection Isn, Condenser Initiation Containment Isolation )

Containment Spray l Core Spray  !

GEMAC 1. Rosemount FW Control - No Safety-(Cold Ref. Leg) Transmitter function (90" to 186* TAF)

2. Lo-Lo Lo

• RBCCW Isol ("

Barton switch -

ADS --Interlock ) '

(56" to 186" TAF) ,

3. fuel Zone Post LOCA Level

(-144" to

+180" TAf) i GEMAC 1. 90" to 490" TAF '

Co'd Shutdown Indication (Cold Ref. Leg)

(Wide Range) 4 (1) Alternate RBCCW isolation initiation on itish Drywett Pressure & Lo-Lo Levet.

(2) ADS la not required for rapid depressurization scenarios.

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